Vacuum valve and method of manufacturing the same

Abstract: An object of the present invention is to provide a low cost and highly reliable vacuum valve and a method of manufacturing the same which improve production efficiency and vacuum tight sealing property of the vacuum valve. In the vacuum valve, within a sealed vacuum vassel 100 a pair of separable conductors in center axial direction of the sealed vacuum vassel composed of a stationary conductor 3 and a movable conductor 5 are disposed. The sealed vacuum vessel 100 is sealed in vacuum tight in such a manner that an upper end portion 1A of a hollow cylindrical insulation body 1 is sealed with a flexible member 6 generally called as bellows and a metal end plate 7 by joining a movable conductor side 6A of the bellows 6 to the movable conductor 5 so as to permit separation of the movable conductor 5 from the stationary conductor 3 while maintaining vacuum sealed condition in the vacuum sealed vessel 100 and by joining one end of the metal end plate 7 with the upper end portion 1A of the hollow cylindrical insulation body 1 and the other end thereof with a metal end plate side 6B of the bellows 6, and a lower end portion 1B of the hollow cylindrical insulation body 1 is sealed with the stationary conductor 3 by itself.

Description: Background of the Invention The present invention relates to a vacuum valve and to a method of manufacturing the same which are suitable for improving its vacuum tightness and production efficiency. A vacuum valve which is one of important elements in a vacuum circuit breaker used as circuit breaking portion and is composed by a vacuum vessel constituted by sealing both ends of a hollow cylindrical insulation body with metal end plates and a pair of separable electrodes constituted by a stationary conductor and a movable conductor disposed in the vacuum vessel. One of the electrodes is connected to the statinary conductor and the other end of the stationary conductor extends in vacuum tightness through the metal end plate. The other electrode is secured to one end of the movable conductor and the movable conductor is connected in vacuum tightness to the other metal end plate via a bellows. Further, for the stationary and movable conductors copper was used and since the joining portions with the hollow cylindrical insulation body of the metal end plates are subjected to many stresses and, in particular, by heating stress, a material such as phosphorus deoxidized copper, Fe-Ni alloy and Fe-Ni-Co alloy was used for the metal end plates as disclosed in JP-A-5-41143(1993). The above mentioned parts constituting the vacuum valve are joined by brazing which makes use of a brazing metal as a joining member. The brazing is performed in such a manner that a brazing material is placed between or near the members to be joined, and is heated at more than the melting point of the brazing material in a furnace of non-oxidizing atmosphere such as a vacuum furnace and a hydrogen furnace to melt the brazing material to thereby join the members. Further, TIG welding and plusma welding can be used for joining the parts constituting the vacuum valve. During production of a vacuum valve evacuation and brazing are performed at the same time in a vacuum furnace and the inside of the vacuum valve is evacuated and is vacuum sealed. For example, such method is disclosed in JP-A-59-175521(1984) in which after partially assembling the parts the assembly is sealed in vacuum tight in a vacuum furnace. More specifically, both a stationary electrode, a stationary conductor and a stationary side metal end plate, and a movable electrode, a movable conductor, a metallic bellows and a movable side metal end plate are firstly joined by brazing, subsequently, the stationary side metal end plate and the movable side metal end plate are secondly joined by brazing in a vacuum furnace to the hollow cylindrical insulation body in such a manner that the stationary side metal end plate and the movable side metal end plate sandwich the hollow cylindrical insulation body. After completing the brazing operation silver plating is applied on the respective external connection terminal portions of the stationary and movable conductors. Further, many investigations have been performed for improving vacuum sealing of the vacuum valve until now. JP-B-5-31245(1993) discloses one of such investigation results in which an improvement of the brazing material for the joining member is proposed, and JP-A-2-195618 (1990) discloses another investigation result in which in order to properly guide parts to be sealed a ring shaped brazing member having a plurality of non-continuous projections along both inner and outer circumferences thereof is used. For the purpose of vacuum sealing the inside of the vacuum valve, if the parts are joined through a single brazing operation, no sufficient heat is transmitted through the single brazing operation for joining both the stationary conductor and the stationary electrode, and the movable conductor and the movable electrode, thereby reliable brazing can not be obtained. For this reason, the joining method as explained above was used in which both the stationary electrode, the stationary conductor and the stationary side metal end plate, and the movable electrode, the movable conductor, the metallic bellows and the movable side metal end plate are firstly joined by brazing, subsequently, the stationary side metal end plate and the movable side metal end plate are secondly joined by brazing in a vacuum furnace to the hollow cylindrical insulation body. With such method it is found out that the brazing operation time is prolonged which decreases production effeciency (work efficiency) and increases the production cost of such vacuum valves. Further, in case when silver plating is applied to the connecting portions with the external conductors of the stationary and movable conductors after the brazing operation between the parts, a solvent such as acid and a plating electrolyte are coated on the surface of the connecting portions. However, these materials show corrosive property such that when these corrosive materials remain at the vacuum valve, a significant problem such as the vacuum leakage and the like is caused, therefore the corrosive materials have to be completely removed which requires substantial time and further reduces production effeciency (work efficiency) and further increases production cost of the vacuum valve. Further, when joining the parts constituting the vacuum valve in the vacuum furnace, heat is supplied through radiation to the vacuum valve so as to melt the brazing material of joint member, however copper which is a major constitution material is likely to reflect the radiation heat and absorbs a limited heat so that it takes time for heating the vacuum valve as well as prevents a uniform reditation heat transmission and causes a non-uniform melting of the brazing material of joining member which induces one of causes of vacuum leakage. Further, in the conventional vacuum valve as indicated above since material such as Fe-Ni alloy and Fe-Ni-Co alloy different from the conductor material Cu was used for the metal end plates and further, many constituent parts were required, joint portions which require vacuum tight seal increase which also induces one of causes of vacuum leakage. Further, although with the conventional method, such as one using an improved brazing material of joint member or guiding members by a plurality of projections formed on the joint member, vacuum tight sealing property of the vacuum valve is improved, however, no vacuum valves having a reliable vacuum tight sealing structure are obtained until now. Accordingly, the vacuum tight sealing property of the conventional vacuum valves are still insufficient. The closest prior art EP-A1-0 286 335 discloses a vacuum valve according to the preamble of claim 1. Summary of the Invention An object of the present invention is to provide a low cost and highly reliable vacuum valve and a method of manufacturing the same which improve production efficiency and vacuum tight sealing property of the vacuum valve. For obtaining a vacuum valve which achieves the above object, the vacuum valve according to claim 1 includes a hollow cylindrical insulation body, a pair of separable conductors disposed within the hollow cylindrical insulation body and a flexible member which connects one of the conductors with one end of the hollow cylindrical insulation body in such a manner to permit separation of the one the conductor from the other conductor while maintaining vacuum tightness inside the hollow cylindrical insulation body and wherein the other end of the hollow cylindrical insulation body is sealed in vacuum tight by the other conductor. Further, for obtaining a vacuum valve which achieves the above object, in the vacuum valve according to the present invention, in which a pair of separable conductors are disposed within a hollow cylindrical insulation body and one end side of the hollow cylindrical insulation body is sealed in vacuum tight via an end plate and a bellows, wherein the other end side of the hollow cylindrical insulation body is sealed in vacuum tight via one of the conductors. Further, for obtaining a vacuum valve which achieves the above object, in the vacuum valve according to the present invention in which a pair of separable conductors constituting a stationary conductor and a movable conductor are disposed in a hollow cylindrical insulation body and one end side of the hollow cylindrical insulation body is sealed in vacuum tight via an end plate and a bellows, wherein the other end side of the hollow cylindrical insulation body is sealed in vacuum tight via the stationary conductor. Further, the material of the stationary conductor near the joint portion with the hollow cylindrical insulation body is constituted by a Cu alloy containing 1 ∼ 10wt% Cr. Moreover, the cross sectional area of the stationary conductor near the joint portion with the hollow cylindrical insulation body is varied depending on variation of magnitude of bending moment with respect to distance near at the joint portion. Further, the stationary conductor is provided with a groove at the end thereof which constitutes the joint portion with the hollow cylindrical insulation body as well as provided with an inwardly projecting face into the hollow cylindrical insulation body in comparison with the joining portion between the stationary conductor and the hollow cylindrical insulation body. Further, for obtaining a vacuum valve which achieves the above object, in the vacuum valve according to the present invention in which a pair of separable conductors constituting a stationary conductor and a movable conductor are disposed in a hollow cylindrical insulation body and one end side of the hollow cylindrical insulation body is sealed in vacuum tight via an end plate and a bellows, wherein the other end side of the hollow cylindrical insulation body is sealed in vacuum tight via the stationary conductor and further, at least one of between the stationary conductor and the hollow cylindrical insulation body and between the movable conductor and the hollow cylindrical insulation body is double sealed in vacuum tight. Further, the stationary conductor is provided with at least two joint portions with the hollow cylindrical insulation body and the space between the joint portions is evacuated. Further, for the bellows a plurality of bellows are provided, one ends of the plurality of bellows are joined to the movable conductor, at least one of the other ends of the plurality of bellows is joined to the hollow cylindrical insulation body and the space between the plurality of bellows is evacuated. Further, for obtaining a vacuum valve which achieves the above object, in the vacuum valve according to the present invention in which a pair of separable conductors constituting a stationary conductor and a movable conductor are disposed within a hollow cylindrical insulation body and one end side of the hollow cylindrical insulation body is sealed in vacuum tight via an end plate and a bellows, the other end side of the hollow cylindrical insulation body is sealed in vacuum tight via the stationary conductor, and the joining portion of the stationary conductor with the hollow cylindrical insulation body is joined by making use of a ring shaped brazing member having a first bent portion formed along the inner circumference thereof which is designed to guide the stationary conductor, a second bent portion formed along the outer circumference thereof which is designed to guide the hollow cylindrical insulation body and projections arranged along the circumference thereof at a predetermined internal. Further, for the bellows a plurality of bellows are provided, one ends of the plurality of bellows are joined to the movable conductor and at least one of the other ends of the plurality of the bellows is joined to the hollow cylindrical insulation body by making use of a ring shaped brazing member having a bent portion along the inner circumference thereof which is designed to guide the hollow cylindrical insulation body and projections arranged along the circumference thereof at a predetermined interval. Further, for the bellows a plurality of bellows are provided, one ends of the plurality of bellows are joined to the movable conductor and at least one of the other ends of the plurality of bellows is joined to the end of the metal end plate at the hollow cylindrical insulation body side by making use of a ring shaped brazing member having a first bent portion formed along the inner circumference thereof which is designed to guide the metal end plate, a second bent portion formed along the outer circumference thereof which is designed to guide the hollow cylindrical insulation body, a step portion which is designed to guide at least one of the other ends of the plurality of bellows and projections arranged along the circumference thereof at a predetermined interval. For obtaining a method of manufacturing the vacuum valve of claim 1 which achieves the above object, in the method of manufacturing a vacuum valve according to claim 11, on an end portion of a stationary conductor a first joining member is placed, on which the lower end portion of a hollow cylindrical insulation body is placed, then a movable conductor is inserted into the hollow cylindrical insulation body, and second and third joining members are respectively placed on a bellows joining portion of the movable conductor and the upper end portion of the hollow cylindrical insulation body, then one end of the bellows is placed on the bellows joining portion via the second joining member and one end of a metal end plate is placed on the upper end portion of the hollow cylindrical insulation body via the third joining member, then a fourth joining member is placed on the other end of the metal end plate and the other end of the bellows is placed on the fourth joining member, thereafter the assembly is heated in a vacuum furnace at a temperature more than the melting temperature of the joining members while applying an external pressure onto the bellows joining portion to thereby produce the vacuum valve. Further, at least one of the stationary conductor and the movable conductor is applied of the nickel plating and the stationary conductor and the movable conductor are conductively heated by contacting a heater to the nickel plated portion to produce the vacuum valve. The one end of the hollow cylindrical insulation body is sealed in vacuum tight by the stationary conductor, the conventional metal end plate is eliminated which is connected in vacuum tight to the stationary conductor as well as seals in vacuum tight of the lower end portion of the hollow cylindrical insulation body. Thereby, number of joining portions between parts which constitute the vacuum valve is decreased and the portions which require vacuum tight seal are accordingly limited. As a result, possible vacuum leakage portions are reduced. Further, the cross sectional area of the stationary conductor near the joining portion with the hollow cylindrical insulation body is varied depending on the variation of bending moment thereof with respect to distance to the joining portion as well as the material of the stationary conductor near the joining portion is composed of a Cu alloy containing 1 ∼ 10wt% Cr. Thereby the mechanical strength of that portion is increased by about 40%. As a result, an adverse effect of thermal expansion coefficient difference of the stationary conductor with the hollow cylindrical insulation body is decreased. Further, the stationary conductor is provided with the inwardly projecting face into the hollow cylindrical insulation body in comparison with the joining portion of the stationary conductor with the hollow cylindrical insulation body. Thereby, electrical field concentration at top end portions of the brazed material caused during voltage application is relaxed. Further, at least one between the stationary conductor and the hollow cylindrical insulation body and between the movable conductor and the hollow cylindrical insulation body is double sealed in vacuum tight, in that, at least two joining portions between the stationary conductor and the hollow cylindrical insulation body are sealed in vacuum tight or one ends of a plurality of bellows are sealed in vacuum tight to the movable conductor and at least one of the other ends of the plurality of the bellows is sealed in vacuum tight to the hollow cylindrical insulation body. Thereby, vacuum tightness of the possible vacuum leakage portions is enhanced. Further, the joining portion of the stationary conductor is joined with the hollow cylindrical insulation body by making use of a ring shaped brazing member having a first bent portion formed along the inner circumference thereof which is designed to guide the stationary conductor, a second bent portion formed along the outer circumference thereof which is designed to guide the hollow cylindrical insulation body and projections arranged along the circumference at a predetermined interval. Thereby, evacuation and maintenance of vacuum at the double sealed structure portions are enabled. Further, with the provision of the bent portions the joining portions between parts are strengthened and vacuum tightness of the possible vacuum leakage portions is enhanced. Still further, with this structure the brazing material is uniformly spreaded over the joining portions between the parts and reliable joining portions are obtained. Further, a plurality of bellows are provided, one ends of the plurality of bellows are joined to the movable conductor as well as at least one of the other ends of the plurality of bellows is joined to the hollow cylindrical insulation body by making use of a ring shaped brazing member having a bent portion formed along the inner circumference thereof which is designed to guide the hollow cylindrical insulation body and projections arranged along the circumference thereof at a predetermined interval, and at least one of the other ends of the plurality of bellows is joined to the end of the metal end plate at the side of the hollow cylindrical insulation body by making use of a ring shaped brazing member having a first bent portion formed along the inner circumference thereof which is designed to guide the metal end plate, a second bent portion formed along the outer circumference thereof which is designed to guide the hollow cylindrical insulation body, a step portion which is designed the guide at least one of the other ends of the plurality of bellows and projections arranged along the circumference thereof at a predetermined interval. Thereby, even at the movable conductor side with the double sealing structure vacuum tightness of the possible vacuum leakage portions is enhanced. Further, with the provision of the projections provided on the ring shaped brazing member evacuation and maintenance of vacuum in the space between the plurality of bellows are enabled. Still further, with this structure the brazing material is uniformly spreaded over the joining portions between parts and reliable joining portions are obtained. In the manufacturing of a vacuum valve, on an end portion of a stationary conductor a first joining member is placed, on which the lower end portion of a hollow cylindrical insulation body is placed, then a movable conductor is inserted into the hollow cylindrical insulation body, and second and third joining members are respectively placed on a bellows joining portion of the movable conductor and the upper end portion of the hollow cylindrical insulation body, then one end of the bellows is placed on the bellows joining portion via the second joining member and one end of a metal end plate is placed on the upper end portion of the hollow cylindrical insulation body via the third joining member, then a fourth joining member is placed on the other end of the metal end plate and the other end of the bellows is placed on the fourth joining member, thereafter the assembly is heated in a vacuum furnace at a temperature more than the melting temperature of the joining members while applying an external pressure onto the bellows joining portion to thereby produce the vacuum valve. Thereby, the entire parts of the vacuum valve are assembled in an order beginning from the stationary conductor located at the bottom portion while sandwitching the respective joining members therebetween. As a result, the vacuum valve is produced by a single joining operation. Further, at least one of the stationary conductor and the movable conductor is applied of nickel plating and the stationary conductor and the movable conductor is conductively heated by contacting a heater onto the nickel plated portion. Thereby, the vacuum valve assembly efficiently absorbs the heat from the heater to thereby shorten the heating time thereof and further the silver plating time required for the conventional manufacturing of vacuum valves is also eliminated. As a result, the production time for the vacuum valve is shortened. Brief Description of the Drawings Fig.1 is a vertical cross sectional view illustrating a characteristic structure of one embodiment of vacuum valves according to the present invention ; Fig.2 is a graph illustrating a relationship between size, bending moment and cross sectional area of the joining portion of the stationary conductor in the vacuum valve as shown in Fig.1 ; Fig.3 is a vertical cross sectional view for explaining a manufacturing method of the vacuum valve as shown in Fig.1 ; Fig.4 is a vertical cross sectional view illustrating a characteristic structure of another embodiment of vacuum valves according to the present invention ; Fig.5 is an enlarged view of the lower end joining portion of the hollow cylindrical insulation body in the vacuum valve as shown in Fig.4 ; Fig.6 is an enlarged view of the upper end joint portion of the hollow cylindrical insulation body in the vacuum valve as shown in Fig.4 ; Fig.7 is a perspective view illustrating the structure of one joining member used in one of the joining portions in Fig.6 ; Fig.8 is a perspective view illustrating the structure of another joining member used in the other joining portion in Fig.6 ; and Fig.9 is a perspective view illustrating the structure of still another joining member used in the joining portion in Fig.5. Detailed Description of the Preferred Embodiments Hereinbelow, embodiments of the present invention are explained in detail with reference to the drawings. Fig.1 is a cross sectional view of a vacuum valve illustrating a first embodiment according to the present invention and Fig.2 is a graph illustrating a relationship between size, bending moment and cross sectional area of the joining portion of the stationary conductor as shown in Fig.1. In the vacuum valve according to the present embodiment, within a sealed vacuum vessel 100 a pair of separable conductors in center axial direction of the sealed vacuum vassel composed of a stationary conductor 3 and a movable conductor 5 are disposed. The sealed vacuum vessel 100 is sealed in vacuum tight in such a manner that an upper end portion 1A of a hollow cylindrical insulation body 1 is sealed with a flexible member 6 generally called as bellows and a metal end plate 7 by joining a movable conductor side 6A of the bellows 6 to the movable conductor 5 so as to permit separation of the movable conductor 5 from the stationary conductor while maintaining vacuum sealed condition in the vacuum sealed vessel 100 and by joining one end of the metal end plate 7 with the upper end portion 1A of the hollow cylindrical insulation body 1 and the other end thereof with a metal end plate side 6B of the bellows 6, and a lower end portion 1B of the hollow cylindrical insulation body 1 is sealed with the stationary conductor 3. To one end of the stationary conductor 3 a stationary electrode 2 is joined and the other end thereof is provided with a connection use threaded portion 3F for connecting an external conductor (not shown), thereby a rod shaped conductor is formed which extends from the stationary electrode 2 and through the stationary conductor 3 to a stationary side electrical contacting face 3E which permits current flow therethrough. The stationary side electrical contacting face 3E of the stationary conductor 3 is formed in an umbrella shape extending radially, at the end of the radially extended portion a groove 3C is formed, and through the formation of the groove 3C, a joining base portion 3B and a joining end portion 3A, which is permitted to join with the lower end 1B of the hollow cylindrical insulation body 1 at the top thereof, are formed. The problem caused by thermal expansion coefficient difference of the materials at the joining portion is controlled by reducing the thickness of the joining end portion 3A near at the joining portion. However, such thickness reduction causes decrease of mechanical strength of those portions, therefore in the present embodiment in order to obtain a required mechanical strength for the portion near the joining end portion 3A a reenforced copper of Cu alloy containing 1∼ 10wt% Cr is used therefor. Further, the cross sectional area (S) of from the joint base portion 3B to the joint end portion 3A is gradually decreased from the joint base portion 3B depending on the variation of bending moment (M) acting thereon with regard to the distance (1) from the joint base portion 3B to the joint end portion 3A as illustrated in Fig.2. More specifically, the thickness reduces gradually from the thickness t1 at the joint base portion 3B to the thickness t2 at the top of the joint end portion 3A. Further, at the center axis side of the groove 3C a projecting face 3D which projects toward the stationary electrode 2 more than the joining end portion 3A is formed, and further an inclining portion 3G having expanded diameters which extends into the center portion of the stationary conductor 3 from the projecting face 3D is formed. Still further, on the surface of the stationary conductor 3 nickel plating is applied. At one end of the movable conductor 5 a movable electrode 4 is jointed and at the other end thereof a connection use threaded portion 5F is provided which is for connecting with an external conductor (not shown), thereby a rod shaped conductor is formed which extends from the movable electrode 4 and through the movable conductor 5 to a movable side electrical contacting face 5E which permits current flow therethrough. At the intermediate portion of the movable conductor a bellows protection shield 5A projecting outwardly is constituted having a larger outer diameter than that of the metallic bellows 6, and at the root portion of the protection a metallic bellows joint portion 5B is provided which permits joining with a movable conductor side end 6A of the metallic bellows 6. Further, the movable conductor 5 is made of a reenforced copper of Cu alloy containing 1∼ 10wt% Cr like that near the joining end portion 3A of the stationary conductor 3 as explained above and is also plated by nickel like the stationary conductor 3 as explained above. The metallic bellows 6 is provided with the movable conductor side end 6A at one end thereof which is adapted to be joined with the bellows joining portion 5B and a metal end plate side end 6B at the other end which is adapted to be joined with the movable conductor side metal end plate 7. The movable conductor side metal end plate 7 is adapted to join with the metal end plate side end 6B of the metallic bellows 6 at the inner circumference thereof and with the upper end 1A of the hollow cylindrical insulation body 1 at the outer circumference thereof. Further, a shield 8 surrounding the stationary electrode 2 and the movable electrode 4 is supported by the inner wall of the hollow cylindrical insulation body 1. Now, a manufacturing method of the above explained vacuum valve is explained with reference to Fig.3. Namely, the vacuum valve is manufactured according to the following steps. I . The stationary conductor 3 is fitted into a lower supporting stand 31 incorporating a heater 32 inside thereof while contacting the stationary side electrical contacting face 3E thereto and above the stationary conductor 3 a brazing member 10 and the stationary electrode 2 are fitted. II . On the joint end portion 3A a ring shaped brazing member 11 and the lower end portion 1B of the hollow cylindrical insulation body 1 are placed successively and the hollow cylindrical insulation body 1 is also fitted into the lower supporting stand 31. III . From above of the hitherto assembled body the movable conductor 5 fitted with a brazing member 12 and the movable electrode 4 therebelow is inserted until the movable electrode 4 contacts the stationary electrode 4 and is supported thereby. IV . Then, on the upper end portion 1A of the hollow cylindrical insulation body 1 a brazing member 15 and the movable conductor side metal end plate 7 are placed. V . On the metallic bellows joint portion 5B of the movable conductor 5 a brazing member 13 and the movable conductor side end 6A of the metallic bellows 6 are placed, then, on the upper portion of the inner circumference of the movable conductor side metal end plate 7 a brazing member 14 is placed as well as the metal end plate side end 6B of the metallic bellows 6 is placed thereon. VI . Under the above explained assembled condition, an upper center pressing metal piece 33 is inserted which presses the movable conductor side end 6A of the metallic bellows 6 and the brazing member 13 while heating the same, further another upper pressing metal piece 34 is placed onto the movable side metal end plate 7, the brazing member 14 and the metal end plate side end 6B of the bellows 6 while pressing and heating the same. VII . The thus assembled assembly is heated once in a vacuum furnace at a temperature more than the melting temperature of the brazing members to complete a vacuum valve. According to the present embodiment, since the stationary conductor 3 integrates upto the joint end portion 3A, the heat absorption of the stationary conductor 3 is improved by nickel plating the wide area covering from the stationary side electrical contacting face 3E to the joint end portion 3A and the stationary conductor 3 is directly heated through conduction by the heater 32, the stationary conductor 3 absorbs heat efficiently. Accordingly, a part of the large amount of heat supplied from the heater 32 is used for melting the brazing member 11 at the joint end portion 3A, and a major portion of the large amount of heat flows through the inclined portion 3G of the stationary conductor 3 having a large cross sectional area and is used for melting the brazing member 10 at the stationary electrode 2 as well as can heat the brazing member 12 at the movable electrode 4 contacting to the stationary electrode 2 for melting the same. Further, since the heat absorption of the movable conductor 5 is also improved by nickel plating the wide area of the movable conductor 5 covering from the movable conductor side electrical contacting face 5E to the metallic bellows joint portion 5B and the upper center pressing metal piece 33 presses directly by its weight the movable conductor side end 6A of the metallic bellows 6, the heat absorbed by the upper center pressing metal piece 33 of radiation heat in vacuum is absorbed into the movable conductor 5 through the nickel plated face of the movable conductor 5, and the contacting portion between the movable conductor side end 6A of the metallic bellows and the upper center pressing metal piece 33, and the brazing member 13 is melted as well as the brazing member 12 at the movable electrode 4 is heated and melted. Through the heating both from upper and lower sides the brazing members 10, 12 and 13 at the inside of the hollow cylindrical insulation body 1 are reliably melted to thereby reliably join the parts through a single joining operation. Further, because of a shortened heating time as well as a shortened work time, the production effeciency is improved, and in addition because of a uniform heat application to the respective joining portions a complete joint can be achieved. Further, according to the present embodiment, with the integration upto the joint end portion 3A of the stationary conductor 3 namely, metal end plate at the statinary conductor side end portion of the hollow cylindrical insulation body is eliminated through the integration of the stationary conductor 3 and the metal end plate, the number of joining portions between parts which require vacuum tightness is reduced. Thereby, possible vacuum leakage portions are reduced and vacuum tightness of the vacuum valve is improved. Further, in the stationary conductor 3 the cross sectional area (S) of from the joint base portion 3B to the joint end portion 3A is gradually decreased from the joint base portion 3B depending on the variation of bending moment (M) acting thereon with regard to the distance (1) from the joint base portion 3B to the joint end portion 3A as illustrated in Fig.2. More specifically, the thickness reduces gradually from the thickness t1 at the joint base portion 3B to the thickness t2 at the top of the joint end portion 3A. Further, a reenforced copper of Cu alloy containing 1 ∼ 10wt% Cr is used for the stationary conductor 3 near at the joining portion with the hollow cylindrical insulation body 1 the mechanical strength of those portions of the stationary conductor 3 is reenforced by about 40% in comparison with pure copper conductors. Thereby, the thickness t2 of the joint end portion 3A of the stationary conductor 3 is thinned by about 40%. Accordingly, even when a pressing force is acted on to the movable conductor side metal end plate 7 while fixing the stationary side electrical contacting face 3E as stationary plane and bending moments are respectively applied to the joint base portion 3B having thickness t1 and to the joint end portion 3A having thickness t2 of the stationary conductor 3, because of the above provision the influence due to thermal expansion coefficient difference between the hollow cylindrical insulation body 1 and the joint end portion 3A is reduced, thereby a possibility of break-down of the joint portion is reduced. Further, the thickness of the joint end portion of the stationary conductor 3 can be easily adjusted by modifying the configuration of the groove 3C. Further, the tops of the melted brazing member at the upper end 1A and the lower end 1B of the hollow cylindrical insulation member 1 are likely to be pointed, and during voltage application, electric field concentrates therearound to generate corona discharge in the vacuum valve which likely causes dielectric breakdown of the vacuum valve. However, according to the present embodiment, the projecting face 3D of the stationary conductor 3 is designed to project inwardly beyond the lower end 1B of the hollow cylindrical insulation body 1, the electric field at the top end portions of the melted brazing member during the volatge application is relaxed, the crona discharge starting voltage thereat is raised and the dielectric break-down of the vacuum valve is prevented. Further, according to the present embodiment, like the stationary conductor 3 the reenfoeced copper of Cu alloy containing 1∼ 10wt% Cr is likely used for the movable conductor 5, therefore the mechanical strength of the movable conductor 5 is likely reenforced, and the possible deformation due to a large mechanical force during circuit making and breaking operation can also be reduced. Further, according to the present embodiment, since the nickel plating is applied to the stationary conductor 3 and the movable conductor 5 before assembling stage thereof and the nickel plating never scatters at the brazing temperature of the brazing members, the nickel plating maintains its electrical contacting function even after the sealing operation in the vacuum furnace and no plating is needed which was required after the sealing operation in the conventional manufacturing process. Such that the manufacturing process of the vacuum valve is shortened, namely the production efficiency is improved, and as a matter of course the conventional problems such as remain of plating solution is eliminated. Further, since the nickel plating shows a good wettability with the brazing materials, in particular, with a commonly used silver series brazing material, highly reliable joints both at the portions requiring vacuum tightness and at the portions requiring current conduction. Still further, nickel shows two time higher withstand voltage than that of copper in vacuum, the dielectric distance between the shield 8 and the stationary conductor 3 or the movable conductor 5 is shortened, thereby the diameter of the vacuum valve can be reduced and the size of the vacuum valve is also reduced. In the present embodiment, through the use of the above explained structure and the manufacturing method, the production efficiency and vacuum thightness of the vacuum valve are improved. However, the vacuum thightness of vacuum valves can also be improved through the use of the following structure which is explained with reference to Fig.4 through Fig.9. Fig.4 is a cross sectional view of the vacuum valve, Fig.5 is an enlarged view of a joining portion 16 between the lower end portion 1B of a hollow cylindrical insulation body 1 and a stationary conductor 3, Fig.6 is an enlarged view of a joining portion 17 between an upper end portion 1A of the hollow cylindrical insulation body 1 and a movable conductor metal end plate 7 and Fig.7 through Fig.9 are perspective views of respective brazing members used as joining member for the present embodiment. In the present embodiment the same and equivalent elements as in the previous embodiment are denoted by the same reference numerals and the explanation thereof is omitted. In the vacuum valve according to the present embodiment, one of the constitutional parts, bellows is constituted in a double structure, in that, constituted by a movable conductor side bellows 6 and a hollow cylindrical insulation body side bellows 6'. In the movable conductor side bellows 6 among these two belows, the metal end plate side end 6B is joined at one end of the movable conductor side metal end plate 7 (the opposite end from that joined to the upper end portion 1A of the hollow cylindrical insulation body 1) along the inner circumference thereof and the movable conductor side end 6A is joined to the bellows joining portion 5B of the movable conductor 5. In the hollow cylindrical insulation body side bellows 6' the metal end plate side end 6'B is joined to the upper end portion 1A of the hollow cylindrical insulation body 1 and the movable conductor side end 6'A is also joined to the bellows joining portion 5B of the movable conductor 5. On the bellows joining portion 5B of the movable conductor 5, a step is formed which corresponds to the thickness required when the movable conductor side end 6'A of the hollow cylindrical insulation body side bellows 6' is brazed and the movable conductor side end 6A of the movable conductor side bellows 6 and the movable conductor side end 6'A of the hollow cylindrical insulation bellows 6' are respectively brazed while applying a predetermined pressing force P. For joining the metal end plate side end 6'B of the hollow cylindrical insulation body side bellows 6' with the upper end portion 1A of the hollow cylindrical insulation body 1 a ring shaped movable conductor side inner brazing member 26 is used. The movable conductor side inner brazing member 26 is provided with an inner circumferential bent portion 20 which is designed to firmly guide the entire circumference of the upper end portion 1A of the hollow cylindrical insulation body 1 and a plurality of projections 23 which are designed to form gaps for evacuating the inside of the vacuum sealed vessel 100. The projections 23 are formed in a recess and projection shape along the circumference of the hollow cylindrical insulation body 1 at a predetermined interval. The outer circumferential portion of the movable conductor side metal end plate 7 is joined on the metal end plate side end 6'B of the hollow cylindrical insulation body 6' via a ring shaped movable conductor side outer brazing member 25. The movable conductor side outer brazing member 25 is provided with an outer circumferential portion 21 which is designed to firmly guide of the entire circumference of the upper end portion 1A of the hollow cylindrical insulation body 1, an inner circumferential bent portion 20 which is designed to guide the inner circumference of the movable conductor side metal end plate 7, a step portion which is designed to guide the outer circumferences of the movable conductor side inner brazing member 26 and the metal end plate side end 6'B of the hollow cylindrical insulation body side bellows 6' and a plurality of projections 23 which are designed to form gaps for evacuating the inside of the vacuum sealed vessel 100. The projections 23 are formed in a recess and projection shape along the circumference of the hollow cylindrical insulation body 1 at a predetermined interval. The radial width of the ring shaped outer movable side brazing member 25 constituting the joining portion 17 between the movable conductor side metal end plate 7 and the upper end portion 1A of the hollow cylindrical insulation body 1 is selected so as to extend from the outer circumference of the upper end portion 1A of the hollow cylindrical insulation body 1 to the inside of the metal end plate 7 and to cover the outer surface of the metal end plate side end 6'B of the hollow cylindrical insulation body side bellows, 6' thereby the surfaces of the upper end portion 1A and the metal end plate side end 6'B are continuously coated with the brazing material after the brazing operation. Further, in the present embodiment, the stationary conductor side electrical contacting face 3E of the stationary conductor 3 is formed by extending in an umbrella shape and at the end thereof the groove 3C is provided. With this groove 3C projections 3H at the end thereof are formed which are to be joined in ring shapes with the lower end portion 1B of the hollow cylindrical insulation body 1, and the projections 3H and the lower end portion 1B of the hollow cylindrical insulation body 1 are joined via a ring shaped stationary conductor side brazing member 22. The ring shaped stationary conductor side brazing member 22 is provided with an outer circumferential bent portion 21 which is designed to firmly guide of the entire circumference of the lower end portion 1B of the hollow cylindrical insulation body 1, an inner circumferential bent portion 20 which is designed to firmly guide the entire circumference of the projection 3H and a plurality of projections 23 which are designed to form gaps for evacuating the inside of the vacuum sealed vessel 100. The projections 23 are formed in a recess and projection shape along the circumference of the hollow cylindrical insulation body 1 at a predetermined interval. Further, the vacuum valve according to the present embodiment is manufactured by making use of substantially the same manufacturing method as explained in connection with the previous embodiment. According to the present embodiment, the bellows, one of the constitutional members of the vacuum valve is constituted in a double structure, in that, constituted by the movable conductor side bellows 6 and the hollow cylindrical insulation body side bellows 6' and at the end portion of the stationary conductor 3 the groove 3C is formed, thereby the vacuum tight sealing portion is doubled and possible vacuum leakage portions are strengthened. Accordingly, the vacuum tightness of the vacuum valve according to the present embodiment is further enhanced in comparison with the vacuum valve according to the previous embodiment. Further, with the provision of the projections 23 formed in recess and projection shape along the circumference of the hollow cylindrical insulation body 1, the space in the groove 3C at the end portion of the stationary conductor 3 and the space surrounded by the movable conductor side bellows 6, the hollow cylindrical insulation body side bellows 6' and the movable conductor side metal end plate 7 are evacuated as well as the inside of the sealed vessel 100 during heating and evacuating operation. Further, since the movable conductor side inner brazing member 26 is provided with the inner circumferential bent portion 20 which is designed to firmly guide the entire circumference of the upper end portion 1A of the hollow cylindrical insulation body 1 as well as the movable conductor side outer brazing member 25 is provided with the outer circumferential bent portion 21 which is designed to firmly guide the entire circumference of the upper end portion 1A of the hollow cylindrical insulation body 1, the inner circumferential bent portion 20 which is designed to guide the inner circumference of the movable conductor side metal end plate 7 and the step portion 24 which is designed to guide the circumferences of the movable conductor side inner brazing member 26 and the metal end plate side end 6'B of the hollow cylindrical insulation body side bellows 6', the joining portion 17 of the metal end plate side end 6'B of the hollow cylindrical insulation body side bellows 6', the upper end portion 1A of the hollow cylindrical insulation body 1 and the movable conductor side metal end plate 7 is kept under a predetermined condition, in that, vacuum sealed condition even if the movable conductor 5 is moved. Accordingly, vacuum inside the sealed vacuum vessel is maintained whicth is very advantageous for a vacuum valve which is used under a condition requiring frequent switching operation. Further, since substantially the same manufacturing method as explained in connection with the previous embodiment is used for the present embodiment, the joining opertation can be completed reliably by a single joining work. Further, because of a shortened heating time as well as a shortened work time, the production effeciency is improved, and in addition because of a uniform heat application to the respective joining portions a complete joint can be achieved. Since the vacuum valve according to the present invention is constituted as thus explained, number of parts constituting the vacuum valve is decreased and correspondingly joint portions requiring vacuum tight seal are reduced, thereby vacuum tightness of the vacuum valve is improved. Further, through the double sealing structure at joining portions of the parts and the improvement of the brazing members constituting the joining member the vacuum tightness of the vacuum valve is further improved. Further, according to the present invention, the properties of absorption and conduction of heat which are required for melting the joining members of brazing material are improved, the dielectric break down in the vacuum valve and damages of the hollow cylindrical insulation body are prevented, the degree of deformation of the movable conductor subjected to during circuit making and breaking operation is limited and the size of the vacuum valve is reduced. Further, the vacuum valve of the present invention is manufactured according to the manufacturing method as explained, the working process is shortened, working time is shortened because of shortened heating time (by a single joining operation) and through the uniform heat application to the joining portions the production effeciency of the vacuum valve is improved. Accordingly, with the present invention a low cost and a highly reliable vacuum valve and the manufacturing method thereof are provided.

Claims: A vacuum valve in which a pair of separable conductors (3, 5) constituting a stationary conductor (3) and a movable conductor (5) are disposed in a hollow cylindrical insulation body (1), and in which one end side of said hollow cylindrical insulation body (1) is sealed in vacuum tight via an end plate (7) and a bellows (6) connected between said movable conductor (5) and said end plate (7), characterized in that the other end side of said hollow cylindrical insulation body (1) is sealed in vacuum tight by said stationary conductor (3), wherein said stationary conductor (3) is provided with a groove (3C) at the end thereof which constitutes the joint portion (3A) with said hollow cylindrical insulation body (1). A vacuum valve according to claim 1, characterized in that the material of said stationary conductor (3) near the joint portion (3A) with said hollow cylindrical insulation body (1) is constituted by a Cu alloy containing 1 ∼ 10 wt% Cr. A vacuum valve according to claim 1, characterized in that the cross sectional area of said stationary conductor (3) near the joint portion (3A) with said hollow cylindrical insulation body (1) is varied depending on the variation of the magnitude of the bending moment with respect to the distance near the joint portion. A vacuum valve according to claim 1, characterized in that said stationary conductor (3) is provided with an inwardly projecting face (3D) into said hollow cylindrical insulation body (1) in comparison with the joining portion (3A) between said stationary conductor (3) and said hollow cylindrical insulation body (1). A vacuum valve according to claim 1, characterized in that at least one of the joints between said stationary conductor (3) and said hollow cylindrical insulation body (1) and between said movable conductor (5) and said hollow cylindrical insulation body (1) is double sealed in vacuum tight. A vacuum valve according to claim 5, characterized in that said stationary conductor (3) is provided with at least two joint portions (3H) with said hollow cylindrical insulation body (1), and that the space (3C') between the joint portions (3H) is evacuated. A vacuum valve according to claim 5, characterized in that a plurality of bellows (6, 6') are provided, wherein one end (6A, 6'A) of each of the plurality of bellows (6, 6') is joined to said movable conductor (5) and at least one (6'B) of the other ends of the plurality of bellows (6, 6') is joined to said hollow cylindrical insulation body (1), and that the space between the plurality of bellows (6, 6') is evacuated. A vacuum valve according to claim 1, characterized in that the joining portion (3A) of said stationary conductor (3) with said hollow cylindrical insulation body (1) is joined by making use of a ring shaped brazing member (22) having a first bent portion (20) formed along the inner circumference thereof which is designed to guide said stationary conductor (3), a second bent portion (21) formed along the outer circumference thereof which is designed to guide said hollow cylindrical insulation body (1) and projections (23) arranged along the circumference thereof at predetermined intervals. A vacuum valve according to claim 8, characterized in that a plurality of bellows (6, 6') are provided, wherein one end (6A, 6'A) of each of the plurality of bellows (6, 6') is joined to said movable conductor (5) and at least one (6'B) of the other ends of the plurality of bellows (6, 6') is joined to said hollow cylindrical insulation body (1) by making use of a ring shaped brazing member (26) having a bent portion (20) along the inner circumference thereof which is designed to guide said hollow cylindrical insulation body (1) and projections (23) arranged along the circumference thereof at predetermined intervals. A vacuum valve according to claim 8, characterized in that a plurality of bellows (6, 6') are provided, wherein one end (6A, 6'A) of each of the plurality of bellows (6, 6') is joined to said movable conductor (5) and at least one (6'B) of the other ends of the plurality of bellows (6, 6') is joined to the end of said metal end plate (7) at said hollow cylindrical insulation body side by making use of a ring shaped brazing member (25) having a first bent portion (20) formed along the inner circumference thereof which is designed to guide said metal end plate (7), a second bent portion (21) formed along the outer circumference thereof which is designed to guide said hollow cylindrical insulation body (1), a step portion (24) which is designed to guide at least one (6'B) of the other ends of the plurality of bellows (6, 6') and projections (23) arranged along the circumference thereof at predetermined intervals. A method of manufacturing the vacuum valve of claim 1, comprising the steps of placing on an end portion of the stationary conductor (3) a first joining member (11); placing on the first joining member (11) the lower end portion (1B) of the hollow cylindrical insulation body (1); then inserting the movable conductor (5) into the hollow cylindrical insulation body (1); placing second and third joining members (13, 15) respectively on the bellows joining portion (5B) of the movable conductor (5) and the upper end portion (1A) of the hollow cylindrical insulation body (1); then placing one end (6A) of the bellows (6) on the bellows joining portion (5B) via the second joining member (13); placing one end of the metal end plate (7) on the upper end portion (1A) of the hollow cylindrical insulation body (1) via the third joining member (15) ; then placing a fourth joining member (14) on the other end of the metal end plate (7); placing the other end of the bellows (6B) on the fourth joining member (14); thereafter heating the assembly in a vacuum furnace at a temperature more than the melting temperature of the joining members (11, 13, 14, 15) while applying an external pressure onto the bellows joining portion (5B) to thereby produce the vacuum valve. The method of claim 11, characterized in that at least at one of the stationary conductor (3) and the movable conductor (5) a nickel plating is applied, and that the stationary conductor (3) and the movable conductor (5) are conductively heated by contacting a heater with the nickel plated portion to produce the vacuum valve.

Inventors: HAKAMATA YOSHIMI, KOBAYASHI MASATO, KOMURO KATSUHIRO, OSAKA AKIRA, TANIMIZU TORU, HAKAMATA, YOSHIMI, KOBAYASHI, MASATO, KOMURO, KATSUHIRO, OSAKA, AKIRA, TANIMIZU, TORU
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1994
Main classification: H01H33
IPC codes: H01H1, H01H33, H01H11